Field of the Invention
The invention relates to metal terminals of the type which are soldered to hybrid integrated circuit substrates for connecting substrates to a circuit board.
A hybrid integrated circuit is a micro-circuit formed by attaching discrete components and semiconductor devices to networks of passive components and conductors that have been vacuum deposited in this film on glazed ceramic, sapphire, or glass substrates. These substrates are generally rectangular. Arranged along their longer edges are a number of contact pads in the form of conducting film rectangles spaced from each other and extending almost to the edge. In order to connect the substrate to an ordinary circuit board, a number of terminals are clipped to the edge of the substrate in contact with the pads. They are soldered in place and fastened to the circuit board by means of stems which include pins for insertion in holes in the board. A particular substrate may have anywhere from several to fifty or more terminals of this type attached to it. Since there are many different kinds of hybrid integrated circuits in use today, terminals of this type are used in very large numbers.
There are various different designs for hybrid integrated circuit terminals which reflect efforts to reduce one or more common problems in using them. Such problems usually involved either the failure of a particular terminal to make adequate contact to its contact pad or the shorting together of adjacent terminals to each other by the unintentional flow of solder between their respective contact pads during the soldering process.
One for of such a terminal which is generally referred to as a "solder bearing" is designed so that a solder pre-form is held in a contact finger prior to assembly of the terminal of the substrate. This provides a precisely measured amount of solder for making the bond upon heating after assembly. There is a continuing need to improve the design of hybrid integrated circuit terminals for better reliability and structural integrity.